1. As always… OWL Lon-Capa assignments Lecture videos Textbook Read
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2. Office Hours 3014 Chemistry Annex decoste@illinois.edu
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3. To Improve: The Obvious
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Textbook
Read it and do the homework.
Videos
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Electronic Homework
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Lon-Capa HW#1: 99%
Lon-Capa HW#3: 92%

4. To Improve: The Less Obvious
Lecture
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Textbook
Read critically, before lecture (take notes, ask questions).
Videos
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Electronic Homework
Do the assignments as you learn about the material.

5. To Improve: The Not Obvious
Change how you view homework.
It is not just something to be over with.
Change how you view studying.
You are currently studying for the second exam whether you believe it or not.
Change how you view learning.
Do it for understanding not for points (and you’ll earn both!).
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6. NH4NO3(s)  NH4+(aq) + NO3–(aq) ΔH = 25.7 kJ
Clicker Question
A g sample of NH4NO3(s) is dissolved in mL of water with both substances initially at room temperature (24.7°C). Calculate the final temperature of the solution. You may make the following assumptions: no heat loss to the surroundings; the specific heat capacity of the solution is 4.18 J/g°C; and the density of water is 1.00 g/mL.
NH4NO3(s)  NH4+(aq) + NO3–(aq) ΔH = 25.7 kJ
a) 17.0°C
b) 17.7°C
c) 31.7°C
d) 32.4°C
e) I cannot get any of these answers.

7. Determining Hrxn
Since H = qp, determine the heat given off or required at constant pressure by measuring temperatures. This is termed calorimetry.
Since energy is conserved, we can often determine Hrxn for one reaction given values of Hrxn for others. Uses the principle in Hess’s Law.
Use standard enthalpies of formations for reactants and products (we have tables of these).

8. Hess’s Law Due to first law and H being a state function.
If a reaction is reversed, the sign of H is also reversed
The magnitude of ΔH is directly proportional to the quantities of reactants and products in a reaction.
That is, if the coefficients in a balanced equation are multiplied by an integer, the value of H is multiplied by the same integer.

9. 2NaHCO3(s)  Na2CO3(s) + CO2(g) + H2O(l)
Clicker Question
Baking soda can decompose to produce sodium carbonate, carbon dioxide, and water according to the following chemical equation:
2NaHCO3(s)  Na2CO3(s) + CO2(g) + H2O(l)
Given the following data, determine ΔH° for the decomposition of baking soda as written above.
Na2CO3(s) + 2HCl(aq)  2NaCl(aq) + CO2(g) + H2O(l) ΔH° = –28.9 kJ/mol
NaHCO3(s) + HCl(aq)  NaCl(aq) + CO2(g) + H2O(l) ΔH° = 28.3 kJ/mol
a) –0.6 kJ b) kJ c) kJ d) kJ e) kJ

10. Determining Hrxn
Since H = qp, determine the heat given off or required at constant pressure by measuring temperatures. This is termed calorimetry.
Since energy is conserved, we can often determine Hrxn for one reaction given values of Hrxn for others. Uses the principle in Hess’s Law.
Use standard enthalpies of formations for reactants and products (we have tables of these).

11. Clicker Question
Using the following data, calculate the standard enthalpy of formation of the compound ICl(g), in kJ/mol:
H° (kJ/mol)
Cl2(g)  2Cl(g) 242.3
I2 (g)  2I(g) 151.0
ICl(g)  I(g) + Cl(g) 211.3
I2(g)  I2(s) –62.8
a) –14.6 b) – c) – d) e) 33.5